Holasteroida

The pourtalesiids (Pourtalesiidae) are a family of irregular sea urchins that live in the deep sea. They are secondarily bilateral-symmetrical and like other representatives of the taxon Holasteroida they lack the lantern of Aristotle, which is typical for many other sea urchins. The genus Pourtalesia was named after Louis-François de Pourtalès who first collected these animals while dredging at a depth of 600 m. The family is known already from the Upper Cretaceous (Maastrichtian) and is distributed worldwide.

Echinocorys is an extinct genus of echinoids that lived from the Late Cretaceous to the Paleocene. The genus belongs to the Holasteridae family. Its remains have been found in Asia, Europe, Australia (Oceania) and North America.

Urechinidae is a family of echinoderms belonging to the order Holasteroida.

Pourtalesia is a genus of the family Pourtalesiidae which belongs to the irregular (bilaterally symmetrical) sea urchins. The animals measure 5–6 cm in length and live in the abyssal zone of the Atlantic, Pacific, Indopacific and Antarctic Oceans where they have been found in more than 3,000 m depth. The mouth opening of these animals is located anteriorly and the lantern of Aristotle is missing as typically for holasteroid sea urchins.

Calymnidae is a family of echinoderms belonging to the order Holasteroida.

Plexechinus is a genus of echinoderms belonging to the monotypic family Plexechinidae.

Holasteroida is an order of irregular sea urchins.

species of echinoderm

species of echinoderm

Hemipneustes is an extinct genus of sea urchins belonging to the family Holasteridae.

species of echinoderm

Holasteridae is an extinct family of sea urchins.